1. Field of the Invention
The present invention relates to a miniature brushless motor used in, for example, micro machinery and precision medical equipment.
2. Description of Related Art
Conventional small cylindrical motors with an outer diameter of approximately 5 mm have been used as eccentrically weighted vibrating motors built in mobile communication devices, such as pagers, personal handy phone systems, and mobile phones, or as drive motors mounted in multi-motored precision equipment, such as office automation equipment, optical instruments, and radio-controlled model vehicles. Moreover, demands for minimized diameter and length are intensifying year by year due to the increasing demand in recent years for ultra-small motors primarily intended to be mounted in precision medical equipment, such as endoscopes or high-tech industrial equipment.
However, the smaller a motor, the more mechanically difficult it is to route the wiring, such as power feed wires, from the power supply side. For ultra-small diameter motors, in particular with an outer diameter of 3 mm or smaller, it is critically important to optimize power feed wiring structure and the mounting location of each part in motor diameter reduction.
FIGS. 6 and 7 show a motor wherein field coil tap wires 20 of a cup-shaped or bell-shaped multiphase field coil 19 are connected to power feed lands of a flexible substrate 22 via connection terminals 21. The strip-shaped protrusions of the flexible substrate 22 extending in the outer radial direction are bent to be accommodated in the concave portions of cutouts 23 provided on one outer peripheral end of a housing 18. Thus, elimination of any protrusion in the outer radial direction of the housing allows diameter minimization. The resulting advantages are significant especially for motors with an outer diameter of 2 mm or smaller (See Reference 1).
As illustrated in FIG. 8, an approximate annular-shaped mounting substrate 27 for holding a flexible substrate 25 having power feed lands for connecting field coil tap wires 26 to an external power supply is fixedly disposed onto one end of a field coil 24, while concave grooves 28 are provided on the outer periphery of the mounting substrate 27 to adhesively hold the field coil tap wires 26. Thus, the mounting substrate 27 doubles as a holder for the field coil tap wires 26 and as a connection relay point to the flexible substrate 25, thereby reducing the likelihood of wire breakage, facilitating connection work to the external power supply, and improving assembly efficiency (See Reference 2).    Reference 1: Japanese Patent Publication No. 2000-166157    Reference 2: Japanese Patent Publication No. 2003-284278